Fluoro Nitrenoid Complexes FN=MF₂ (M=Co, Rh, Ir): Electronic Structure Dichotomy and Formation of Nitrido Fluorides N≡MF₃

Abstract

The fluoronitrenoid metal complexes FNCoF 2 and FNRhF 2 as well as the first ternary Rh VI and Ir VI complexes NIrF 3 and NRhF 3 are described. They were obtained by the reaction of excited Group-9 metal atoms with NF 3 and their IR spectra, isolated in solid rare gases (neon and argon), were recorded. Aided by the observed 14/15 Ni sotope shifts and quantum-chemical predictions,a ll four stretching fundamentals of the novel complexes were safely assigned. The F À N stretching frequencies of the fluoronitrenoid complexes FNCoF 2 (1056.8 cm À1)a nd FNRhF 2 (872.6 cm À1)a re very different and their NÀMb onds vary greatly.I nF NCoF 2 ,t he FN ligand is singly bonded to Co and bears considerable iminyl/nitrene radical character,w hile the N À Rh bond in FNRhF 2 is astrong double bond with comparatively strong sand p-bonds.The anticipated rearrangement of FNCoF 2 to the nitrido Co VI complex is predicted to be endothermic and was not observed.

High‐Spin Imido Cobalt Complexes with Imidyl Radical Character**

“…This is increasingly employed for the catalytic amination of unfunctionalized C À H bonds or the aziridation of olefines. [1][2][3][4][5][6][7][8][9][10][11][12] Despite the resulting high demand for understanding late 3d-transition metal imido species, comprehensive knowledge about the electronic and structural factors that contribute to their properties and bond activation reactivity is still lacking. Whereas most isolable imido metal complexes are found in a low-spin state, those with higher spin-states tend to be more reactive.…”

“…[13,14,16,[23][24][25]34] It resembles those of the known 3d-metal imidyl/nitrene compounds (Figure 1) and a matrix-isolated fluoronitroid cobalt species (Co À N 1.77 ), for which imidyl/nitrene character was discussed. [12] Given these comparably long C À N imide bonds found for complexes [2] À and [3] À we were curious if this was connected to the unique anionic character of these imido complexes, [46] as nearly all comparable 3dmetal imido complexes are either neutral or cationic. Thus, the overall neutral cobalt(I) complex K[1] [55] was reacted with Dipp-N 3 and Tripp-N 3 which gave the respective complexes K [2] and K [3].…”

High‐Spin‐Imidocobaltkomplexe mit Imidylradikalcharakter**

“…Dies wird zunehmend für die katalytische Aminierung unfunktionalisierter C-H-Bindungen oder die Aziridierung von Olefinen genutzt. [1][2][3][4][5][6][7][8][9][10][11][12] Trotz des daraus resultierenden hohen Interesses für späte 3d-Übergangsmetallimidspezies fehlt es an umfassenden Kenntnissen über die elektronischen und strukturellen Faktoren, die zu ihren Eigenschaften und ihrer Bindungsaktivierungsreaktivität beitragen. Während die meisten isolierbaren Imidometallkomplexe in einem Low-Spin-Zustand gefunden werden, sind diejenigen mit hçheren Spin-Zuständen tendenziell reaktiver.…”

“…[13,14,16,[23][24][25]34] Die hier beobachtete Bindungslänge ist vergleichbar zu bekannten 3d-Metall-Imidyl-/Nitrenverbindungen (Abbil-dung 1) und einer Matrix-isolierten Fluoronitroid-Cobaltspezies (Co-N 1.77 ), für welche ein Imidyl-/Nitrencharakter diskutiert wurde. [12] Da nahezu alle vergleichbaren 3d-Metallimidokomplexe entweder neutral oder kationisch sind, gingen wir der Frage nach, ob der anionische Charakter für die ungewçhnlich lange Co-N Imid -Bindung der Komplexe [2] À und [3] À verantwortlich ist. Aus diesem Grund wurde der neutrale Cobalt(I)komplex K[1] [55] mit Dipp-N 3 und Tripp-N 3 umgesetzt, was zur Bildung der entprechenden Komplexe K- [2] und K [3] führte.…”